Low cost multiple IPs

I'm trying to find a low cost solution for a client to implement QoS to protect his VOIP lines from bandwidth starvation but there a catch...

The client has a DSL modem and 4 public IP addresses assigned. 3 of those adresses are connected to webservers (accessed for the internet) and the 4th is for general internet use from withing the store.

The RV042 does one-to-on NAT but no QoS, the WRV200 does basic QoS but no one-to-one NAT that I know of (anyways, this product is not yet ready for primetime).

So that leaves us to a good ole WRT54x with a thir party firmware. I know how to add multiple IP addresses to the WAN port but I,M not sure how to forward or NAT them afterward to the correct webservers on the other side since they all use port 80. Also, I need the QoS module to take all that mess into account when prioritizing packets for VOIP...

OK, I've found the undumented QoS page on one of my RV042s but it is interface based instead of being application based. I supose I could plug the VOIP server on one LAN port and give it "HIGH" priority and plug the rest on other LAN ports and give them "NORMAL" priority. I wonder how this type of QoS compares to application based QoS? Anyone tried it?

ifican: For the WRV200s, I have two setup in WDS and I always have to reboot them. I could have used WRT54GLs/DD-WRT for that client but I'm not a big fan of installing non standard solution in business environment. I keep that for myself! Unless one of them has faulty hardware I qualify them as not ready. However, I will check into that more deeply since you said that it is very stable for you.